What are the 10 minerals on the Mohs scale?

From softest to hardest: talc (1), gypsum (2), calcite (3), fluorite (4), apatite (5), orthoclase feldspar (6), quartz (7), topaz (8), corundum (9) and diamond (10). The USGS lists the same order, naming feldspar for 6 and sapphire, a form of corundum, for 9.

What is the hardness of a fingernail, a penny and glass?

The National Park Service lists a fingernail at 2.5, a copper penny at 3.5 and a knife or glass plate at 5.5. Geology.com gives a fingernail as 2 to 2.5, copper sheet as 3, and glass as 4 to 7 depending on the glass. Treat these as approximate field tests.

What is the Mohs hardness of quartz?

Quartz is 7 on the Mohs scale. USGS also gives 7 for quartz as a gemstone, such as amethyst and citrine. That is harder than window glass and a steel nail, so quartz scratches both.

What is the Mohs hardness of jade and other gemstones?

The USGS table used on this page gives jade as 6, turquoise as 5 to 6, opal as 5.5 to 6.5, garnet as 6.5 to 7.5, topaz as 8, corundum (ruby and sapphire) as 9 and diamond as 10. Other references may split jade into jadeite and nephrite with different numbers, so check which material you have.

Is diamond twice as hard as corundum?

No. The Mohs scale is ordinal, so 10 is not twice 5. Wikipedia reports that in absolute hardness diamond is about four times as hard as corundum, even though they are only one step apart on the scale.

Can I trust a scratch test to identify a gemstone?

Use it only as a rough clue. A scratch test damages the sample, results depend on the test tool and the exact stone, and many gems share similar hardness. Gemologists combine hardness with other properties such as density and refractive index, and do not scratch-test finished stones.

Mohs Hardness Scale

See all 10 Mohs hardness levels with minerals, everyday scratch tests and gem hardness, plus a bar chart you can print or edit. Free, no sign-up.

Chart your own hardness data Type label and value rows, then download the bar chart as SVG or PNG.Bar Chart Maker

Scratch test

Pick two materials to see which one scratches the other. The harder material scratches the softer one.

Material A

Material B

Result

Calcite scratches Fingernail

Calcite (3) is harder than Fingernail (2.5), so it leaves a scratch and is not scratched back.

Fingernail: NPS gives 2.5; Geology.com gives 2 to 2.5.

Free Mohs Hardness Scale Charts

Every chart below is drawn from the same code as the tool above. View, download and print them free, no sign-up.

Scale chart

Mohs Hardness Scale Chart: 10 Minerals

Talc to diamond with chemical formulas. Bar length is the Mohs rank, not an absolute hardness.

1 / 6

Charts

Printable versions

Learning about how minerals form? See the rock cycle diagram generator and the plate tectonics diagram generator, or plot your own measurements with the bar chart maker.

What is the Mohs hardness scale?

The Mohs scale ranks minerals by scratch resistance. The German mineralogist Friedrich Mohs devised it, and it uses ten reference minerals from talc (1) to diamond (10). A mineral with a higher number scratches any mineral with a lower number. To place an unknown mineral, find the reference minerals it scratches and the ones that scratch it: a sample that scratches fluorite (4) but is scratched by apatite (5) has a hardness between 4 and 5.

It is an ordinal scale, not a linear one

The numbers only give an order. The step from 1 to 2 is not the same size as the step from 9 to 10. Wikipedia notes that, in absolute hardness, corundum (9) is about twice as hard as topaz (8), while diamond (10) is about four times as hard as corundum. That is why the bar charts on this page show the Mohs rank itself and say so, instead of inventing a spacing.

How to do a scratch test

Pick a clean, fresh surface on the sample and press a point of the test material firmly against it, then drag it about a centimeter. Wipe the area and look closely, ideally with a hand lens: a real scratch is a groove that stays after wiping, while powder from the softer test tool can leave a streak that looks like a scratch but rubs off. Start with a soft tool such as a fingernail (about 2.5) and move up through a copper penny (about 3.5), a knife blade or glass (about 5.5) and a steel nail (about 6.5) until one leaves a mark. Test an edge or a spot that does not matter, and never test a finished gemstone you want to keep.

Why the everyday values are ranges

Sources disagree on common objects because the objects vary. Window glass differs by composition, knife blades and files differ by steel, and a modern penny is mostly zinc, so it behaves differently from the old copper cent. The tables list one value where a source gave one, show a range where it gave a range, and mention the other source in a note. When the ranges of two materials overlap, the scratch test above says they are too close to call.

Hardness is not toughness

Hardness measures resistance to scratching. Toughness is resistance to breaking, chipping or cracking, and it is a different property. Diamond is the hardest natural mineral but can cleave along crystal planes if struck, and jade is famously tough even though it is softer than quartz. A hard gemstone can still chip at an edge. Stability to heat, chemicals and cleavage matters as much as the Mohs number when you choose a stone for a ring.

Frequently Asked Questions

Sources

Hardness numbers on this page were read from the pages below. Formulas and the comparison of absolute hardness come from Wikipedia. Where sources differ, the tables say so.

US National Park Service: Mohs Hardness Scale (The 10 reference minerals and common test objects)
Geology.com: Mohs Hardness Scale (Hardness ranges for common test objects)
USGS: Gemstones, Mineral Hardness (The scale and the hardness of 16 gemstones)
Wikipedia: Mohs scale of mineral hardness (Chemical formulas and a few metal and material values)

Related Science Tools

Research

Bar Chart Maker

Create horizontal, grouped, and stacked bar charts for rankings, comparisons, and classroom data visualization.

Try it free

Earth Science

Rock Cycle Diagram Generator

Create rock cycle diagrams showing igneous, sedimentary, and metamorphic rock transformations for earth science.

Try it free

Earth Science

Plate Tectonics Diagram Generator

Create labeled plate tectonics diagrams with AI: divergent, convergent (subduction), and transform plate boundaries, mantle convection, trenches, and volcanic arcs.

Try it free

Earth Science

Water Cycle Diagram Generator

Generate free printable water cycle diagrams showing evaporation, condensation, and precipitation. Perfect for earth science worksheets.

Try it free

View All Free Tools